Means for constructing joints in concrete roads



Sept. 11, 1962 J. M. cuMMlNGs 3,052,945

MEANS FOR CONSTRUCTING JOINTS IN CONCRETE ROADS 2 Sheets-Sheet 1 FiledJune 16, 1959 a ii si:

INVENTOR. llsse N. C...M` "\S BY M'M'ASnmw-f% Sept. 11, 1962 J, MCUMMlNGs 3,052,945

MEANS FOR CONSTRUCTING JOINTS IN CONCRETE ROADS 2 Sheets-Sheet 2INVENTOR. Tusa M. Cwwu Filed June 16, 1959 T'ORNEXS' United StatesPatent O 3,052,945 MEA-IBIS EGR CNSTRUCTNG JiNTS EN (JNCRE'IE RADS.lesse M. Cummings, Barrington, RJ., assigner, by mesne assignments, toNew England Plastics Corporation,

Waltham, Mass., a corporation of Massachusetts Fiied .lune 16, 1959,Ser. No. 829,755 3 Claims. (Ci. 25-118) This invention relates to theconstruction of concrete roads, airport landing strips and the like andparticularly to methods and means for inducing the formation of cracksin the concrete at intervals to accommodate the dimensional changes inthe strip either during setting or as the result of subsequentvariations in atmospheric temperature.

t has been the common practice to induce the formation of cracks atintervals depthwise through concrete roadway strips for the purposestated, by forming grooves transversely of the strip which extenddepthwise for a fraction of the thickness of the concrete slab but whichdelineate predetermined vertical planes of weakness in or near which theslab is induced to crack through its remaining depth during thesubsequent concrete setting process or during the subsequent temperaturevariations to which the road is exposed. One or more grooves extendinglongitudinally of the axis of the road are also usually provided for thesame purpose and these grooves, whether trans-verse or longitudinal, areiilled with a water prooing mastic, such as asphalt, to seal the base ofthe concrete slab against the infiltration of water and foreignmaterials.

The experience in the art has been that prior known methods and devicesused and proposed for use for this purpose have certain practicaldeficiencies.

Attempts to mold the groove into the concrete by inserting a moldingstrip in the freshly poured mix to be removed after the concrete hasbecome set have presented problems especially in the task of extractingthe strip. The molding strip is left in place until the concrete issufficiently set to prevent collapse of the groove upon removal of thestrip, but its removal after the concrete is cured damages the concreteby disturbing the aggregate in the process of removal. Some moldingstrips have even had to be routed out which is a time consuming andexpensive operation which does further damage to the concrete, ininstances necessitating a subsequent costly hand edging operation. Theexpedient of sawing grooves in the set concrete involves a criticalproblem of timing of the sawing operation. vIf it is done too early inthe curing phase the coarse aggregate will be displaced and its bondwith the matrix broken; but if too late the concrete is apt to crackrandomly which is just what the groove forming operation seeks to avoid.Sawing also is sometimes most impracticable because of the inability toavoid cutting through the coarse aggregate hidden within the concreteslab and which in some areas is extremely resistant to sawing.

Many of the prior art proposals found in the literature, but which havenot gone into use, evidence by their complexities the diiculty ofsatisfactorily accomplishing this simple task of forming the grooves atdesired intervals.

It is the object of the present invention to solve these problems and toprovide a method and means for forming the grooves at the proper time,that is, within a matter of minutes after the pouring is completed,without having to wait until after hours which is the frequent practicewith sawed joints where the operation has to be performed at the rightstage in the setting process and where the rate of cure varies withatmospheric conditions. It is my further purpose to employ a grooveforming device which can be removed without damage to the concrete,which is inexpensive, which can be repeatedly used without wearing out,and which forms a groove of non-varying, exact, dimensions.

In the drawings:

FIG. l is a perspective View of a concrete roadway under construction;

FEG. 2 is a perspective exploded view of one end of my novel grooveforming mold;

FIG. 3 is a view similar to FIG. 2, but showing the spreader in place;

FIG. 3a is an enlarged view ofthe apex of the groove forming mold;

FIG. 4 is a diagrammatic side elevation view of the inserting jaws;

FIG. 5 is a vertical section of the upper portion of the concrete slab,showing the mold fully inserted;

FIG. 6 is a vertical section corresponding to FIG. 5, but with theinserting mechanism out of the way;

FIG. 7 shows the mold with its side walls converged after the wedge hasbeen removed;

FIG. 8 is a diagrammatic view of the groove that is formed, with themold removed;

FIG. 9 is a view corresponding to FIG. 8 showing the groove lled withmastic, and

FlG. l0 is a view showing the crack formation.

Referring to FIG. l, the reference numeral 2 shows a roadway that hasbeen poured between the side forms 4 and 6. The numerals 8, 9 and 1t?designate successive grooves that have been formed according t0 myinvention and 3 designates a longitudinal center groove. At 12,superimposed over the location for the next succeeding transversegroove, is indicated diagrammatically the inserting and retractingmachine which is supported on wheels 14 riding on the form 4 as a trackand on corresponding wheels (not shown) on the opposite side riding onform 6 as a track. In this way the machine 12 -bridges the road and mayreadily be moved along to successive groove locations.

Machines of the type suggested diagrammatically at 12 for inserting agroove forming mold are known and available in the industry. Theparticular kind of machine forms no part of my present invention, exceptas hereinafter indicated, and in FIG. 4 I have shown diagrammaticallyenough of the machine for an understanding of my present invention, aswill be referred to below.

My novel joint former or wedge 15, as shown in its preferred embodimentin FIGS. 2 and 3 is composed of two parts, a mold 26, which is V-shapedin vertical section, and a spreader 22. The mold 20 has a pair of sidewalls 24; and 26, joined at an apex juncture 28. It is made of a waterand caustic-resistant material such as vinyl resin extruded from a diein the form of the V. The spreader 22, molded of the same material, hastapered sides 2S and 34) of a predetermined angular divergence to bedescribed and has a top 32 formed with side flanges 34 and 36 protrudingoutwardly from the sides 2S and 3% respectively a distance approximatingthe thickness of the side walls 24 and 26 of the mold so that, when thespreader is in place, fully inserted between the side walls 24 and 25,as in the assembled View, FIG. 3, the flanges rest on the upper edges ofthe side walls of the mold, thus limiting the extent of the insertion,and forming a smooth, uninterrupted continuation of the outer surfacesof the side walls. When fully inserted the lower blunt edge 38 of thespreader is substantially midway of the depth of the mouth internallyseparating the side walls 24 and 26 of the mold.

The joint former, composed of mold and spreader, may be of anyconvenient length for use in forming the longitudinal groove 8, rangingfrom perhaps l0 feet to l5 feet. For use in forming transverse grooves Ihave found that joint formers in lengths varying between l1 feet'and 12feet accommodate the most frequently occurring slab widths of 1l, 12,22, 24 or 25 feet, but the length can, of course, be varied as desired,and when two are needed to t crosswise between the forms 4 and 6 themachine 12 usually inserts Vthem simultaneously, holding them inalignment between the inserting jaws.

The jaws of the inserting machine 12 are represented diagrammatically inFIG. 4 at 4t) and 42, shown holding a joint former mold 2% and aspreader 22 in position above the surface S of the freshly pouredconcrete. The jaws are suitably constructed to open and close forinsertion and release of the joint former. They are vibrated in adirection laterally of the groove to be formed, as indicateddiagrammatically by arrows and FIG. 4 shows, for that purpose, aneccentric 52 mounted on bracket 54 carried by jaw 42 and suitably powerdriven.

As'soon as the concrete has been poured and given a suitable surfacingtreatment, the machine 12, with one or more joint formers insertedbetween its jaws 40 and 42 is accurately positioned for the formation ofthe groove along the desired line. The vibrating mechanism is startedand as the jaws are lowered the joint former works its way into therwetconcrete. The coarse aggregate as Ywell as the fines are pushed aside,as shown in FIG. 5 and the jaws d@ and 42 push their way, with the jointformer, below the surface Sii of the concrete until the upper surface ofthe top 32 of the spreader is I; inch or so below the surface 56 of theconcrete. The jaws 40 and i2 of the inserting machine then retract,opening as necessary, to leave the joint former in place. The jaws neednot disturb the concrete unduly, during the process, as they can be madeof thin metal, almost knife-like in thickness, and when they retract themix readily lls the void, aided by the further surface finishingoperation which then follows. Alternatively some inserting machineseject the joint former from between the jaws which then can be limitedin their downward travel so as not to enter the concrete.

After the insertion of the joint former the further surface finishing isby a conventional tlat float drawn over the joint area at right anglesto it. This may leave a thin layer of concrete over the top 32 as shownat 61 in FiG. 6. The concrete displaced by the joint former, spread oversay 1/2 foot from the joint line in both directions, represents only asmall fraction of an inch added thickness as the increased density ofthe concrete resulting from the vibration uses most of it.

The concrete is then allowed to set and the joint former should be leftin place usually for at least 18 hours and longer if the settingconditions are slow.

At any convenient time thereafter, but preferably not until the joint isto be completely finished, the joint former is removed and until it isremoved the groove in the concrete which it has formed is effectivelysealed against dirt and moisture.

The facility of the operation of removal is a feature of my invention.The T-shaped spreader is first removed by lifting it straight up,starting with the form on one side, and this permits the side walls ofthe mold to snap together free of the side wals of the groove as shownin FIG. 7. The mold may then readily be lifted out leaving the opengroove 60, FIG. 8. The next operation is to lill the groove with amastic 62, such as asphalt, FIG. 9. The joint is then complete and iseffective to predetermine a plane of weakness vertically of the concreteso that the slab cracks through its full thickness in that plane, asindicated at 64 in FIG. 10 and this crack will occur either during thecuring or setting process or occasionally during subsequent changes inatmospheric temperature. Y

The thickness of the side walls 24 and 26 of my novel mold is adequateto preserve the planar outer surface of the side walls Vagainstdistortion under the compression of the surrounding wet concrete mix,especially in the areas of the side walls between the portions supportedby the spreader 22 and the apex. The thickness vertically of thematerial at the apex juncture may be of the order of two or more timesthe thickness of the walls as shown at X in FIG. 3a to assure that theside walls have a rcsiliency which forces them to snap inwardly, asshown in FIG. 3, upon removal of the spreader 22. The spreader isconformingly tapered to force the side walls `apart against theresiliency of the material at the apex as shown in FIG. 3, so that theouter surfaces of 4the mold form a groove preferably of taperingconguration.y The V- shaped groove which the mold forms is ofnon-varying volume and dimensions from joint to joint and by its V shapeaccurately predetermines the position in which the crack thereafterforms. The depth of the groove is desirably about 2 inches for mostroadwork and perhaps 3 inches for airlields and the ratio of .the depthof groove to the total thickness of the concrete is preferably of theorder of from about 1 tot 5 to about 1 to 7. The taper in `theembodiment illustrated is from about inch lat the mouth to about 1A;inch at the base of 'the groove.

I claim:

l. A two-member wedge, comprising extruded elements, for forming agroove in freshly poured concrete, one member, of resilient material,being formed with two sidewalls extending upwardly `from an yapexjuncture at the bottom, the thickness laterally of the sidewalls, inproximity to the juncture, being adequate to withstand, without internalsupport, the compression of surrounding wet concrete mix, the said apexjunctureV being formed with a thickness vertically at leastapproximately twice the said thickness laterally `of the sidewalls toaford rigidity at the apex by which the Wedge may ybe driven into theconcrete -without internal support at `the apex and lto impart acontractual elasticity to the sidewalls forcing them from a divergingposition to a position in which the ,sidewalls are substantially incontact with each other, the second member being wedge-shaped andinserted between the upper edges of the sidewalls of the irst member tohold them in said diverging position.

2. A two-member wedge, comprising extruded elements, for yforming agroove in freshly poured concrete, one member, `of resilient material,being formed with two sidewalls extending upwardly from yan apexjuncture at the bottom, the thickness laterally of the sidewalls, inproximity to the juncture, being adequate to withstand, without internalsupport, the compression of surrounding wet concrete mix, the said apexjuncture being formed with a thickness vertically at least`approximately twice the said thickness laterally of the sidewalls toaiford rigidity at the apex by which the wedge may be driven into theconcrete without internal support at the apex and to impart acontractual elasticity to the sidewalls forcing them from a divergingposition to la position in which the sidewalls are substantially incontact with each other, the second member being wedge-shaped andinserted between the upper edges of the sidewalls of the first member tohold them in said diverging position, and having a shoulder to cooperatewith a said upper sidewall edge to llimit the depth of insertion of saidsecond member within said iirst member.

3. The `device as defined in claim 2 wherein the said first member isformed of a rust-and-corrosion resistant,

Water-insoluble synthetic plastic.

References Cited in the hle of this patent UNITED STATES PATENTS1,596,179 Heltzel Aug. 17, 1926 1,697,563 Heltzel Jan. 1, 1929 1,768,838Heltzel July 1, 1930 1,850,512 Lytle Mar. 22, 1932 1,851,615 Bishop Mar.29, 1932 1,863,846 Heltzel June 21, 1932 2,961,731 Buzzell NOV. 29, 1960...NN when( 'n

